This invention relates to heat exchangers, including oil coolers of the so-called xe2x80x9cdoughnutxe2x80x9d type that can be used separately or in conjunction with oil filters in automotive and other engine and transmission cooling applications and heat exchangers or oil coolers having a rectangular shape. This invention also relates to manifolds for the transfer and distribution of two fluids, particularly heat exchanging fluids.
Oil coolers have been made in the past out of a plurality of stacked plate pairs located in a housing or canister. The canister usually has inlet and outlet fittings for the flow of engine coolant into and out of the canister circulating around the plate pairs. The plate pairs themselves have inlet and outlet openings and these openings are usually aligned to form manifolds, so that the oil passes through all of the plate pairs simultaneously. These manifolds communicate with oil supply and return lines located externally of the canister. An example of such an oil cooler is shown in Japanese Utility Model Laid Open Publication No. 63-23579 published Feb. 16, 1988.
Where the oil cooler is used in conjunction with an oil filter, the plate pairs are usually in the form of an annulus and a conduit passes through the center of the annulus delivering oil to or from the filter located above or below the oil cooler and connected to the conduit. The oil can pass through the filter and then the oil cooler, or vice-versa. Examples of such oil coolers are shown in U.S. Pat. Nos. 4,967,835 issued to Thomas E. Lefeber and 5,406,910 issued to Charles M. Wallin.
A difficulty with these prior art heat exchangers (HXs) however is that they have limited performance efficiency. This limitation is exacerbated in applications where compact HX configurations are required. In particular, in prior art HXs at least one of the fluids must be circulated through the stack plate passages in a circumferential, or split-flow circumferential flow direction. This results in a high flow resistance, or pressure drop for this fluid. Also, the necessity to include relatively large fluid ports within prime regions of the plate area that could otherwise be used for heat transfer, detracts from overall performance or compactness. Thirdly, there are inherent flow distribution problems with one or all of the fluids being distributed around, or between the plate heat transfer passages, which are difficult to overcome in prior art designs. Finally, to maximize heat transfer efficiency it is desirable to achieve a true counter-flow direction between the two fluids, yet this is impractical in prior art constructions. In these cases, the two fluids flow at essentially perpendicular directions.
The present invention provides a high performance compact heat exchanger in which the two fluids can have a true parallel flow direction including counterflow direction and yet low pressure drop. Further the HXs described herein can achieve extremely uniform flow distribution according to the flow conditions required, and a graduation means to control this in changing section, or irregular shaped HXs. There is also provided a novel manifold that allows flexibility in locating external fluid connections, while providing a low pressure drop and balanced flow distribution interface with the HX internal fluid distribution manifolds.
The present invention is expected to have particular applicability to compact automotive heat exchangers, including oil/water transmission and engine oil heat exchangers and other high performance liquid to liquid or liquid to gas heat exchangers. The present invention offers particular benefits for refrigerant to water (or other liquid) HX""s in as much as two phase fluids are normally particularly sensitive to flow maldistribution effects, both within the heat exchange passages and the connection manifolds, and which the present invention overcomes.
More specifically, a preferred embodiment of the present invention is a high performance, plate type compact HX based on structural provision of cross-over passages that intersect internal fluid distribution manifolds. These cross-over passages allow both fluids to be directed in a short path, counterflow relationship. A low pressure drop is simultaneously achieved for both fluids, based on the resultant short paths, and by judicious selection of appropriate heat transfer augmentation means.
In one preferred version of the invention, there is a deliberate adjustment of the size and shape of fluid transfer apertures that are arranged in groupings to allow parallel flow distribution, the adjustment being used to achieve uniform flow distribution across the plate surfaces, and over a range of HX shapes.
A preferred embodiment of the present invention is a heat exchanger having a self-enclosing configuration, ie without the need for an external housing to contain one of the fluids. If desired, the invention can still be used in a form having an external xe2x80x9ccanxe2x80x9d or housing that contains the heat exchanger.
Optional design features of these HXs are also described that include a fluid passage to allow partial bypassing of one fluid, in the case that an excess flow supply needs to be accommodated, and internal cones to improve flow distribution.
The heat exchanger of the present invention is very efficient with relatively low pressure drop. In one version of the present heat exchanger employing mating ringlike plates which are placed in a stack, the two heat exchanging fluids are able to travel radially so the two fluid flows are parallel to one another. Thus, the first heat exchanging fluid can flow radially through inner flow passages formed between the plates while a second heat exchanging fluid is able to flow through outer flow passages formed between back-to-back plate pairs. In another version of the heat exchanger of the invention which can employ generally rectangular plates, again, the two heat exchanging fluids are able to flow in inner and outer flow passages in parallel directions.
In one version of the invention employing ringlike or annular plates and annular primary and secondary bosses, radially extending ribs are formed about the circumference of one or more of the primary bosses and extend substantially across their respective boss. These ribs are located between and separated from openings formed in their respective primary bosses and they form cross-over passages that permit one of the heat exchange fluids to flow radially across the primary bosses and through inner flow passages. In a rectangular embodiment of the heat exchanger, each plate in the stack is formed with first and second elongate primary ridges and at least one secondary ridge and at least a portion of the primary ridges have ribs extending transversely across the width of the ridge and distributed along the length thereof. Again, these ribs are located between and separated from openings formed in the primary ridges and form cross-over passages that permit one of the heat exchanging fluids to flow transversely across the primary ridges and through inner flow passages.
According to one aspect of the invention, a heat exchanger comprises an plurality of stack plate pairs consisting of face-to-face, mating ringlike plates, each plate having a peripheral flange and annular inner and outer primary bosses each having a portion thereof located in a common first plane with the peripheral flange. Each plate also has an annular secondary boss having a portion thereof located in a second plane spaced from the first plane and parallel thereto. Intermediate areas are located between the inner and outer primary bosses and the peripheral flanges and the primary bosses in the mating plates are joined together. The intermediate areas of each plate pair have spaced-apart portions to form an inner flow passage between the plates. The secondary boss is located adjacent to one of the primary bosses and on a side thereof furthest from the other of the primary bosses. Both the primary bosses and the secondary bosses have openings formed therein for passage of first and second heat exchanging fluids respectively. The secondary bosses are arranged such that in back-to-back plate pairs, the secondary bosses are joined and the respective openings therein communicate to define a manifold for the flow of the second heat exchanging fluid. The intermediate areas of back-to-back plate pairs define outer flow passages therebetween. The primary bosses of at least one plate of each pair include radially extending ribs formed about the circumferences of at least one primary boss and extending substantially across the respective primary boss. These ribs are located between and separated from the openings formed in the primary boss and form cross-over passages so that the cross-over passages of each plate pair permit the secondary heat exchange fluid to flow across its respective primary bosses and through its respective inner flow passage.
In the preferred version of this heat exchanger, the peripheral flange is an outer peripheral flange located radially outward from the primary and secondary bosses and the secondary boss is an outer secondary boss located radially outwards from its respective outer primary boss. There are also flow augmentation means preferably located in both of the inner flow passages and the outer flow passages.
According to another aspect of the invention, a heat exchanger for heat transfer between first and second heat exchanging fluids includes a plurality of stacked plate pairs consisting of face-to-face mating plates, each plate having edge flanges extending along edges thereof and first and second spaced-apart elongate primary ridges each having a portion thereof located in a common first plane with the at least one of the edge flanges. Each plate also has an elongate secondary ridge having a portion thereof located in a second plane spaced from the first plane and substantially parallel thereto. The secondary ridge is provided between an adjacent one of the edge flanges and the first primary ridge of the respective plate. An intermediate area is located between the first and second primary ridges and these areas of each pair have spaced-apart portions to form an inner flow passage between the plates. Both the primary ridges and the secondary ridge have openings formed therein for the passage of the first and second heat exchanging fluids respectively. The secondary ridges are arranged such that in back-to-back plate pairs, the secondary ridges are joined and the respective openings therein communicate to define a manifold for the flow of the second heat exchanging fluid. The intermediate areas of back-to-back plate pairs have spaced-apart portions defining outer flow passages therebetween. The primary ridges of at least one plate of each pair include ribs extending across the width of at least one primary ridge of the at least one plate and distributed along the length of the primary ridge. These ribs are located between and separated from the openings formed in the primary ridge and form cross-over passages so that the cross-over passages of each plate pair permit the secondary heat exchanging fluid to flow transversely across its respective primary ridges and through its respective inner flow passage.
Again, this heat exchanger preferably includes flow augmentation means located in both of the inner flow passages and the outer flow passages.
According to still another aspect of this invention, there is provided a manifold for the transfer and distribution of two fluids (such as two heat exchanging fluids) which may be used in conjunction with the aforementioned heat exchanger which employs mating ringlike plates. This manifold comprises a pair of manifold plates consisting of face-to-face, mating ringlike plates each having inner and outer peripheral flanges and substantially annular inner and outer bosses projecting in the same direction from a first plane defined by the outer peripheral flange. Each plate also includes a substantially annular intermediate channel located between the inner and outer bosses and having openings for passage of a first fluid between the two intermediate channels. At least one of the intermediate channels has radial ribs formed about the circumference of the channel and extending substantially across the channel. These ribs are formed between and separated from the openings formed in the channel and form cross-over passages that permit a second fluid to flow in a radial direction between the inner and outer bosses. At least one of the outer bosses has at least one port formed for the passage of the second fluid into or out of a sealed first space formed between the two outer bosses. There are also means extending over one side of the pair of manifold plates for sealingly enclosing the adjacent intermediate channel of the manifold plates. This enclosing device has one or more apertures formed therein and forms a flow passage for the fluid to flow between the openings in the intermediate channels and the one or more apertures. The inner boss of one of the pair of manifold plates has holes for the passage of the second fluid into or out of a sealed second space formed by the two inner bosses.
In the preferred manifold, the enclosing device is a third plate and the first and second fluids are heat exchanging fluids for carrying out heat exchange in a heat exchanger.
Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings.